To perform optical communication or the like, an optical module equipped with a light emitting device or a light detecting device serving as an optical device is connected to a transmitting optical fiber for transmitting optical signals. The distal end of the transmitting optical fiber must be accurately positioned in relation to the optical device. For this purpose, a plug for connecting the transmitting optical fiber to the optical module is attached to the distal end portion of the transmitting optical fiber, and the plug is coupled to the optical module so as to position the distal end of the transmitting optical fiber in relation to the optical device of the optical module. An example of the configuration of such an optical module and a plug or an optical coupler equipped with the optical module and the plug will be described with reference to FIG. 5.
FIG. 5 shows the configuration of a conventional optical coupler. As illustrated in FIG. 5, an optical coupler 400 is equipped with a light emitting module 200 and a plug 300. The light emitting module 200 has a package 202. The package 202 is an approximately hexahedral housing that opens upward. Installed in the package 202 is a silicon substrate 204. A semiconductor laser device 206 is fixed at a predetermined position of the top surface of the silicon substrate 204.
The light emitting module 200 is provided with a connecting optical fiber 208 and a ferrule 210. The connecting optical fiber 208 is an optical fiber that has been cut to a predetermined length, the end surface at one side being fixed between the silicon substrate 204 and a holding plate 212 such that it is positioned in relation to the light emitting portion of the semiconductor laser device 206.
The end at the other side of the connecting optical fiber 208 is secured in the ferrule 210 with an adhesive agent so that an end surface 208a, which has been polished to have a convex spherical surface, juts out of the ferrule 210. The ferrule 210 is secured to the package 202 via a flange 210a that has been integrally formed therewith.
Formed on one end of the package 202 is a pair of recessed portions 202a and 202a that open outwardly. The recessed portions 202a and 202a are used for coupling the plug 300. The top open part of the package 202 is covered with a lid which is not shown and which is installed after completing the assembly of the light emitting module 200.
The plug 300 is provided with a housing 302 and a ferrule 304. The plug 300 is attached to the distal end portion of the transmitting optical fiber by inserting the distal end portion of a transmitting optical fiber cable C to be connected, a sheath of the distal end portion being removed, into the ferrule 304 and by securing it therein. The distal end portion of the transmitting optical fiber is also polished to have a convex spherical surface and disposed so that it juts out of the ferrule 304.
The housing 302 has a pair of engaging portions 302a and 302a that engage the recessed portions 202a of the package 202 to couple the housing 302 to the package 202.
The optical coupler 400 is configured such that, when the engaging portions 302a are engaged with the recessed portions 202a to couple the light emitting module 200 to the plug 300, the distal end of the ferrule 210 of the light emitting module 200 is brought near the distal end of the ferrule 304 of the plug 300. Then, the distal end 208a, which has the convex spherical surface, of the connecting optical fiber 208 is abutted against the distal end, which has the convex spherical surface, of the transmitting optical fiber. The distal ends of the ferrule 210 and 304 are inserted in a cylindrical split sleeve 306 to align the ferrules 210 and 304 and to also align the distal end 208a, which has the convex spherical surface, of the connecting optical fiber 208 with the distal end, which has the convex spherical surface, of the transmitting optical fiber.
A light detecting module equipped with a light detecting device as an optical device also has a like configuration.